Most integrated circuits are designed to operate using a specific power supply voltage range. For example, a memory device may be designed to operate using a nominal 12 volt supply, and a range of .+-.5% or .+-.10%. If the integrated circuit were designed to use an internal voltage less than the supply voltage, the supply voltage is often regulated with internal circuitry to produce the lower voltage level. Certain integrated circuits have different externally supplied voltages for specific functions. For example, a FLASH memory device may receive an externally supplied voltage to program a floating gate memory cell.
The need for higher supply voltages is reduced as integrated circuit process technologies are developed to reduce the size of components, such as transistors. These components cannot handle the such high voltage levels without sustaining damage. For compatibility with prior devices, however, new integrated circuits should be capable of operating at the previous supply voltage levels. To reduce the supply voltage to a level which is desired, a transistor can be coupled to the supply voltage. The transistor, coupled as a diode, is designed to have a breakdown voltage which exceeds the supply voltage level. In an integrated circuit where the components are designed to handle lower voltages, additional process steps and masks are required to fabricate a transistor capable of handling a high voltage. That is, the transistor would require special process considerations, such as a thicker gate oxide and/or a larger gate and/or different source/drain implants.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a voltage reduction circuit which allows a new generation of an integrated circuit to be compatible with voltage levels used in prior generations, while eliminating additional process steps.